Human renal organic anion transporter 1 (hOAT1) and its role in the nephrotoxicity of antiviral nucleotide analogs

A case of Fanconi syndrome that developed following a year of consumption of a red yeast rice supplement

Although some dietary supplements have been reported to cause renal dysfunction, there have been few reports of supplement-induced Fanconi syndrome. We present the case of a 56-year-old woman with Fanconi syndrome that developed after she consumed a red yeast rice supplement. She was referred to our hospital because of renal dysfunction, and was found to have electrolyte abnormalities, including hypophosphatemia and hypouricemia, renal diabetes, and hyperchloremic metabolic acidosis, and was, therefore, diagnosed with Fanconi syndrome. Renal biopsy revealed proximal tubular injury characterized by severely degenerated tubular epithelial cells as well as mild hypocellular fibrosis. We speculated that the red yeast rice supplement, which the patient had been consuming for approximately 1 year, might be a cause of her syndrome, because reports of renal dysfunction associated with the consumption of red yeast rice supplements have emerged in Japan since 2024. After the supplement was discontinued and oral prednisolone treatment was initiated, the patient's renal function improved and her electrolyte abnormalities were ameliorated. Furthermore, even after tapering off and discontinuing the prednisolone over approximately 12 weeks, her renal function remained. Because Fanconi syndrome may be caused by various exogenous substances, the taking of a thorough medical history is crucial, including with respect to the use not only of prescription medications, but also other substances, including supplements.

Molecular mechanisms underpinning the protection against antiretroviral drug-induced sperm-endocrine aberrations and testicular toxicity: A review

The introduction of highly active antiretroviral therapy (HAART) has revolutionized the treatment of HIV/AIDS worldwide. The HAART approach is the combination of two or more antiretroviral drugs of different classes and are responsible for patient's survival and declining death rates from HIV/AIDS and AIDS-related events. However, the severe and persistent reproductive side effect toxicity of HAART regimens is of great concern to patients within the reproductive age. Till date, the underlying pathophysiology of the HAART-induced reproductive toxicity remains unraveled. Nevertheless, preclinical studies show that oxidative stress and inflammation may be involved in HAART-induced sperm-endocrine deficit and reproductive aberrations. Studies are emerging demonstrating the efficacy of plant-based and non-plant products against the molecular alterations and testicular toxicity of HAART. The testicular mechanisms of mitigation by these products are associated with enhancement of testicular steroidogenesis, spermatogenesis, inhibition of oxidative stress and inflammation. This review presents the toxic effects of HAART on spermatogenesis, reproductive hormones and testis integrity. It also provides insights on the molecular mechanisms underlying the mitigation of HAART testicular toxicity by plant-based and non-plant agents. However, effect of repurposing clinical drugs to combat HAART toxicity is unknown, and more mechanistic studies are evidently needed. Altogether, plant-based and non-plant products are potential agents for prevention of rampant endocrine dysfunction and testicular toxicity of HAART.

Metabolism Pathways of Major Therapeutics for Treating Monkeypox Mono- and Co-infection with Human Immunodeficient Virus or SARS-CoV-2

Monkeypox is a zoonotic viral disease and remains endemic in tropical regions of Central and West Africa. Since May of 2022, cases of monkeypox have soared and spread worldwide. Confirmed cases have shown no travel history to the endemic regions as seen in the past. The World Health Organization declared monkeypox a global public health emergency in July 2022, and the United States government followed suit one month later. The current outbreak, in contrast to traditional epidemics, has high coinfection rates, particularly with HIV (human immunodeficiency virus), and to a lesser extent with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the pathogen of COVID-19. No drugs have been approved specifically for monkeypox. However, there are therapeutic agents authorized to treat monkeypox under the Investigational New Drug protocol, including brincidofovir, cidofovir, and tecovirimat. In contrast to limited options for monkeypox treatment, there are available drugs specifically for HIV or SARS-CoV-2 infection. Interestingly, these HIV and COVID-19 medicines share metabolism pathways with those authorized to treat monkeypox, particularly of hydrolysis, phosphorylation, and active membrane transport. This review discusses how these pathways shared by these medicines should be considered to gain therapeutic synergy and maximize safety for treating monkeypox coinfections.

Risk Factors of Renal Tubular Dysfunction in Thai People Living with HIV Receiving Tenofovir Disoproxil Fumarate

Tenofovir disoproxil fumarate (TDF) associates with renal tubular dysfunction (RTD) in some people living with HIV (PLWH). We studied clinical and genetic factors associated with RTD in Thai PLWH receiving TDF. RTD was diagnosed in 13 of 65 (20%) patients. The median (interquartile range) age and CD4 cell counts were 43.8 (40.4-50.9) years and 554 (437-716) cells/mm³, respectively. The median duration of TDF use was 46.9 (31.5-54.1) months. Univariate logistic regression demonstrated body mass index (BMI), concomitant use of protease inhibitor (PI), hyperlipidemia, and homozygous C/C SNP rs1059751 of ABCC4 gene as predisposing factors of RTD. In multivariate model, concomitant use of PI [adjusted odds ratio (aOR) 11.39; 95% confidence interval (CI), 1.59- 81.56; P = 0.015], hyperlipidemia (aOR 8.59; 95% CI, 1.46-50.40; P = 0.017), and BMI (aOR 0.76; 95% CI, 0.59-0.98; P = 0.037) remained associated with RTD in patients receiving TDF. PLWH receiving TDF with the presence of these factors should be closely monitored for RTD.

Tenofovir disoproxil fumarate-mediated γ-globin induction is correlated with the suppression of trans-acting factors in CD34+ progenitor cells: A role in the reactivation of fetal hemoglobin

Sickle-cell disease (SCD) and β-thalassemia are public health issues that affect people all over the world. Fetal hemoglobin (HbF) induction is a molecular intervention, including hydroxyurea, which has made an effort to improve current treatment. Tenofovir disoproxil fumarate (TDF) is formerly reported with improving levels of hemoglobin, mean corpuscular hemoglobin (MCH), and mean corpuscular volume (MCV). Hence, in this preclinical investigation, human peripheral whole blood-derived CD34⁺ progenitor cells were cultured to prove the efficacy of TDF on erythroid proliferation, differentiation, γ-globin gene expression regulation, and ultimately HbF production. We observed that TDF increased the proliferation of immature erythroid cells, delayed the terminal erythroid maturation without cytotoxicity as correlated with other HbF inducers. Here, the presented data show that TDF can induce HbF expression by up-regulating the γ-globin gene transcription up to 7.1 ± 0.46-fold and subsequently increased the F-cells (10.79 ± 1.9-fold) population in terminally differentiated erythroid cells. Furthermore, our findings demonstrated that TDF-mediated γ-globin gene induction and HbF production was associated with down-fold regulation of BCL11A and SOX6, and their corresponding trans-acting regulators, FOP, KLF1, and GATA1. Collectively, our findings suggest TDF as an effective inducer of HbF in CD34⁺ cells and pave the way to put forward the assessment of TDF as a new potential therapy in treating β-hemoglobinopathies.

Determinants and Incidence of Chronic Kidney Disease with Tenofovir-Based Antiretroviral Therapy Regimens: A Cohort Study in HIV-Infected Adults in South China

Background:

The data of the impact of tenofovir (TDF) on kidney damage in Chinese HIV-1 infected patients are limited.

Objective:

To evaluate the incidence and risk factors of stage 3 chronic kidney disease (CKD) and rapid kidney function decline (RKFD) among Chinese HIV-1 infected patients starting with a TDF-based regimen.

Method:

We enrolled in 797 TDF-initiated HIV-1-infected patients in a Chinese cohort. Kidney dysfunctions were defined as stage 3 CKD (eGFR < 60 mL/min/1.73 m2 during follow-up) and RKFD (eGFR decline > 10 mL/min/1.73 m2/year). A linear mixed-effects model was used to quantify the average eGFR change per 48 weeks. A generalized estimating equation regression analysis was conducted to determine the risk factors associated with renal dysfunction. The method of multiple imputation was used to reduce the bias caused by missing data.

Results:

In this retrospective study, 14 (2%) patients experienced stage 3 CKD, and 272 (34%) individuals experienced RKFD during a median of 26 (IQR, 4-78; maximum 325) weeks follow-up period. The mean loss in eGFR per 48 weeks increased consistently over time, from -2.59 mL/min/1.73 m2 before 48 weeks to -17.61 mL/min/1.73 m2 after 288 weeks. For every 10 mL/min/1.73 m2 increase of eGFR, the risk of RKFD increased by 29% (95%CI: 18%, 40%). Each 10 years older and every 10 mL/min/1.73 m2 higher in baseline eGFR, the risk of stage 3 CKD increased to 1.56 (95% CI: 1.00, 2.43) and decreased by 65% (95% CI: 48%, 76%), respectively. Anemia and higher viral load were significantly associated with RKFD. The results were robust across a range of multiple imputation analyses.

Conclusions:

TDF-associated CKD is rare in HIV-1 infected Chinese adults. Longer TDF-exposed patients are more likely to have renal dysfunction, especially those with older age, anemia, lower baseline eGFR, and higher viral load.

Drug-Induced Acute Kidney Injury

Medications are a common cause of AKI especially for patients admitted to hospital wards and the intensive care unit. Although drug-related kidney injury occurs through different mechanisms, this review will focus on three specific types of tubulointerstitial injury. Direct acute tubular injury develops from several medications, which are toxic to various cellular functions. Their excretory pathways through the proximal tubules contribute further to AKI. Drug-induced AKI may also develop through induction of inflammation within the tubulointerstitium. Medications can elicit a T cell-mediated immune response that promotes the development of acute interstitial nephritis leading to AKI. Although less common, a third pathway to kidney injury results from the insolubility of drugs in the urine leading to their precipitation as crystals within distal tubular lumens, causing a crystalline-related AKI. Intratubular obstruction, direct tubular injury, and localized inflammation lead to AKI. Clinicians should be familiar with the pathogenesis and clinical-pathologic manifestations of these forms of kidney injury. Prevention and treatment of AKI relies on understanding the pathogenesis and judiciously using these agents in settings where AKI risk is high.

3-year Treatment of Tenofovir Alafenamide vs. Tenofovir Disoproxil Fumarate for Chronic HBV Infection in China

BACKGROUND AND AIMS

Tenofovir alafenamide (TAF) has similar efficacy to tenofovir disoproxil fumarate (TDF) but with improved renal and bone safety in chronic hepatitis B patients studied outside of China. We report 3-year results from two phase 3 studies with TAF in China (Clinicaltrials.gov: NCT02836249 and NCT02836236).

METHODS

Chinese hepatitis B e antigen (HBeAg)-positive and -negative chronic hepatitis B patients with viremia and elevated alanine aminotransferase were randomized 2:1 to TAF or TDF treatment groups and treated in a double-blind fashion for 144 weeks (3 years). Efficacy responses were assessed by individual study while safety was assessed by a pooled analysis.

RESULTS

Of the 334 patients (180 HBeAg-positive and 154 HBeAg-negative) randomized and treated, baseline characteristics were similar between groups. The overall mean age was 38 years and 73% were male. The mean HBV DNA was 6.4 log₁₀ IU/mL. The median alanine aminotransferase was 88 U/L, and 37% had a history of antiviral use. At week 144, the proportion with HBV DNA <29 IU/mL was similar among the two groups, with TAF at 83% vs. TDF at 79%, and TAF at 93% vs. TDF at 92% for the HBeAg-positive and -negative patients, respectively. In each study, higher proportions of TAF than TDF patients showed normalized alanine aminotransferase (via the American Association for the Study of Liver Diseases and the China criteria) and showed loss of HBsAg; meanwhile, the HBeAg seroconversion rates were similar. Treatment was well-tolerated among the TAF patients, who showed a smaller median decline in creatinine clearance (-0.4 vs. -3.2 mL/min; p=0.014) and less percentage change in bone mineral density vs. TDF at hip (-0.95% vs. -1.93%) and spine (+0.35% vs. -1.40%).

CONCLUSIONS

In chronic hepatitis B patients from China, TAF treatment provided efficacy similar to TDF but with better renal and bone safety at 3 years.

Concomitant administration of HAART aggravates anti-Koch-induced oxidative hepatorenal damage via dysregulation of glutathione and elevation of uric acid production

Anti-Koch and HAART have been shown to independently induce toxicity to the liver and kidney, albeit available data are few and inconsistent. The present study evaluates the impact of Anti-Koch and HAART, when administered singly and in combination, on hepatic and renal status, and the possible role of adenine deaminase (ADA)/xanthine oxidase (XO) pathway. Anti-Koch and HAART administration were observed to independently impair hepatic and renal functions, diminish glutathione content, and substantially increase lipid peroxidation (MDA) and nitrogen reactive specie (NO). Coherently, these drugs caused significant accumulation of polymorphonuclear leucocytes, up-regulated ADA/XO signaling, increased uric acid production, and enhanced DNA fragmentation in the liver and kidney. Anti-Koch treatment did not significantly alter hepatic and renal levels of nitric oxide nor induce DNA fragmentation in the kidney. Co-administration of anti-Koch and HAART aggravated the observed biochemical alterations. Findings from the histopathological studies of the liver and renal tissues were in agreement with observed biochemical alterations. In conclusion, this report is the first to reveal that anti-Koch and HAART, when administered singly or in combination, attenuate glutathione content and elevate uric acid production in the liver and kidney via upregulation of ADA/XO signaling with resultant oxidative and nitrosative stress, and increased DNA fragmentation.

Tenofovir disoproxil fumarate induces fetal hemoglobin production in K562 cells and β-YAC transgenic mice: A therapeutic approach for γ-globin induction

Pharmacologic induction of fetal hemoglobin (HbF) is an effective strategy for treating β-hemoglobinopathies like β-thalassemia and sickle cell anemia by ameliorating disease severity. Hydroxyurea is the only FDA-approved agent that induces HbF, but significant nonresponders and toxicity limit its clinical usefulness. This study relates preclinical investigation of Tenofovir disoproxil fumarate (TDF) as a potential HbF inducing agent, using human erythroleukemia cell line and a β-YAC mouse model. Erythroid induction of K562 cells was studied by the benzidine/H₂O₂ reaction, total hemoglobin production was estimated by plasma hemoglobin assay kit, and γ-globin gene expression by RT-qPCR, whereas, fetal hemoglobin production was estimated by flow cytometry and immunofluorescence microscopy. We observed significantly increased γ- globin gene transcription and HbF expression mediated by TDF in K562 cells. Subsequent treatment of β-YAC transgenic mice with TDF confirmed HbF induction in vivo through an increase in γ-globin gene expression and in the percentage of HbF positive red blood cells. Moreover, TDF showed no cytotoxic effect at HbF inducing concentrations. These data support the potential development of TDF for the treatment of hematological disorders, including β-thalassemia and sickle cell anemia.

Spatial Distribution Profiles of Emtricitabine, Tenofovir, Efavirenz, and Rilpivirine in Murine Tissues Following In Vivo Dosing Correlate with Their Safety Profiles in Humans

Emtricitabine (FTC), tenofovir (TFV), efavirenz (EFV), and rilpivirine (RPV) are currently used as components of HIV combination therapy. Although these drugs are widely used in antiretroviral therapy, several organ toxicities related to TFV and EFV have been observed clinically. TFV is associated with nephrotoxicity, whereas EFV-related hepatotoxicity and neurotoxicity have been reported. While the precise molecular mechanisms related to the above-mentioned clinically observed toxicities have yet to be elucidated, understanding the local tissue distribution profiles of these drugs could yield insights into their safety profiles. To date, the distributions of these drugs in tissue following in vivo exposure are poorly understood. Therefore, in this study, we employed a matrix-assisted laser desorption/ionization mass spectrometry imaging method to generate spatial distribution profiles of FTC, TFV, EFV, and RPV in mouse tissues following in vivo dosing of following drug regimens: TFV–FTC–EFV and TFV–FTC–RPV. For this study, liver, brain, kidney, spleen, and heart tissues were obtained from mice (n = 3) following separate oral administration of the above-mentioned drug regimens. Interestingly, EFV was detected in liver, brain, and heart following TFV–FTC–EFV treatment. Additionally, hydroxylated EFV, which encompasses the cytochrome P450-dependent monooxygenated metabolites of EFV, was detected in liver, brain, spleen, and heart tissue sections. Notably, the tissue distribution profiles of RPV and hydroxylated RPV following in vivo dosing of TFV–FTC–RPV were different from EFV/hydroxylated EFV despite RPV belonging to the same drug class as EFV. In conclusion, the observed spatial distribution profiles of the study drugs are in agreement with their safety profiles in humans.

Tenofovir alafenamide use in pregnant and lactating women living with HIV

Introduction: Tenofovir alafenamide (TAF)-containing fixed-dose drug combinations (FDCs) are increasingly being used in managing pregnant women living with HIV. However, TAF is not currently recommended during pregnancy due to limited pharmacokinetic and safety data. TAF, a newer nucleotide phosphonamidate prodrug of tenofovir (TFV), achieves high levels of tenofovir-diphosphate in lymphoid cells and hepatocytes, and 90% lower systemic concentrations of TFV compared to tenofovir disoproxil fumarate (TDF), thereby maximizing TAF's antiviral efficacy, potency and clinical safety.Areas covered: This review discusses the currently available information on the pharmacology of TAF in pregnant women living with HIV. Pharmacokinetic studies with TAF during pregnancy have yielded varying results compared to postpartum, but TAF exposures during pregnancy have been within the range of those typically observed in non-pregnant adults. The efficacy and safety of TAF in treatment-naïve pregnant women living with HIV is currently being evaluated in the VESTED study, a phase-III NIH randomized clinical trial.Expert opinion: Initial pregnancy data suggest that TAF-based FDCs have high efficacy and low risk of adverse effects during pregnancy. TAF is likely to become part of first-line regimens for use in pregnant women living with HIV once additional pregnancy data from phase III trials are available.

Pharmacokinetics, Placental and Breast Milk Transfer of Antiretroviral Drugs in Pregnant and Lactating Women Living with HIV

BACKGROUND

Remarkable progress has been achieved in the identification of HIV infection in pregnant women and in the prevention of vertical HIV transmission through maternal antiretroviral treatment (ART) and neonatal antiretroviral drug (ARV) prophylaxis in the last two decades. Millions of women globally are receiving combination ART throughout pregnancy and breastfeeding, periods associated with significant biological and physiological changes affecting the pharmacokinetics (PK) and pharmacodynamics (PD) of ARVs. The objective of this review was to summarize currently available knowledge on the PK of ARVs during pregnancy and transport of maternal ARVs through the placenta and into the breast milk. We also summarized main safety considerations for in utero and breast milk ARVs exposures in infants.

METHODS

We conducted a review of the pharmacological profiles of ARVs in pregnancy and during breastfeeding obtained from published clinical studies. Selected maternal PK studies used a relatively rich sampling approach at each ante- and postnatal sampling time point. For placental and breast milk transport of ARVs, we selected the studies that provided ratios of maternal to the cord (M:C) plasma and breast milk to maternal plasma (M:P) concentrations, respectively.

RESULTS

We provide an overview of the physiological changes during pregnancy and their effect on the PK parameters of ARVs by drug class in pregnancy, which were gathered from 45 published studies. The PK changes during pregnancy affect the dosing of several protease inhibitors during pregnancy and limit the use of several ARVs, including three single tablet regimens with integrase inhibitors or protease inhibitors co-formulated with cobicistat due to suboptimal exposures. We further analysed the currently available data on the mechanism of the transport of ARVs from maternal plasma across the placenta and into the breast milk and summarized the effect of pregnancy on placental and of breastfeeding on mammal gland drug transporters, as well as physicochemical properties, C:M and M:P ratios of individual ARVs by drug class. Finally, we discussed the major safety issues of fetal and infant exposure to maternal ARVs.

CONCLUSIONS

Available pharmacological data provide evidence that physiological changes during pregnancy affect maternal, and consequently, fetal ARV exposure. Limited available data suggest that the expression of drug transporters may vary throughout pregnancy and breastfeeding thereby possibly impacting the amount of ARV crossing the placenta and secreted into the breast milk. The drug transporter's role in the fetal/child exposure to maternal ARVs needs to be better understood. Our analysis underscores the need for more pharmacological studies with innovative study design, sparse PK sampling, improved study data reporting and PK modelling in pregnant and breastfeeding women living with HIV to optimize their treatment choices and maternal and child health outcomes.

Probenecid-Boosted Tenofovir: A Physiologically-Based Pharmacokinetic Model-Informed Strategy for On-Demand HIV Preexposure Prophylaxis

Multiple doses of tenofovir disoproxil fumarate (TDF) together with emtricitabine is effective for HIV preexposure prophylaxis (PrEP). TDF is converted to tenofovir (TFV) in circulation, which is subsequently cleared via tubular secretion by organic ion transporters (OATs; OAT1 and OAT3). Using in vitro kinetic parameters for TFV and the OAT1 and OAT3 inhibitor probenecid, a bottom‐up physiologically‐based pharmacokinetic model was successfully developed for the first time that accurately describes the probenecid–TFV interaction. This model predicted an increase in TFV plasma exposure by 60%, which was within 15% of the observed clinical pharmacokinetic data, and a threefold decrease in renal cells exposure following coadministration of a 600 mg TDF dose with 2 g probenecid. When compared with multiple‐dose regimens, a single‐dose probenecid‐boosted TDF regimen may be effective for HIV PrEP and improve adherence and safety by minimizing TFV‐induced nephrotoxicity by reducing TFV accumulation in renal cells.

A case of entecavir-induced Fanconi syndrome

Acquired Fanconi syndrome has been associated with the long-term ingestion of several nucleoside analogs used to treat chronic hepatitis B virus infection. However, the nucleoside analog entecavir has not been found to cause nephrotoxicity. We report a case of entecavir-induced Fanconi syndrome. Our patient was a 73-year-old man admitted to our hospital because of renal dysfunction. He also presented with hyperaminoaciduria, renal diabetes, phosphaturia, hypophosphatemia, hypokalemia, hypouricemia, and hyperchloremic metabolic acidosis, supporting a diagnosis of Fanconi syndrome. In this case, the cause of Fanconi syndrome was most likely entecavir, which had been administered as needed depending on his renal function for 5 years. After drug discontinuation and replacement with tenofovir alafenamide fumarate therapy once a week, the patient's kidney function recovered and electrolyte anomalies partially improved. We highlight the fact that entecavir may induce severe renal dysfunction, which can cause the development of Fanconi syndrome; therefore, close monitoring of proximal tubular function is recommended during entecavir therapy.

Pre-exposure Prophylaxis With Tenofovir Disoproxil Fumarate/Emtricitabine and Kidney Tubular Dysfunction in HIV-Uninfected Individuals

BACKGROUND

Pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) is becoming increasingly adopted for HIV prevention. Tenofovir can cause proximal tubular damage and chronic kidney disease in HIV-infected persons, but little is known regarding its nephrotoxic potential among HIV-uninfected persons. In this study, we evaluated the effects of PrEP on urine levels of the following: α1-microglobulin (α1m), a marker of impaired tubular reabsorption; albuminuria, a measure of glomerular injury; and total proteinuria.

SETTING

The Iniciativa Profilaxis Pre-Exposicion (iPrEx) study randomized HIV-seronegative men and transgender women who have sex with men to oral TDF/FTC or placebo. The iPrEx open-label extension (iPrEx-OLE) study enrolled former PrEP trial participants to receive open-label TDF/FTC.

METHODS

A cross-sectional analysis compared urine biomarker levels by study arm in iPrEx (N = 100 treatment arm, N = 100 placebo arm). Then, urine biomarker levels were compared before and after PrEP initiation in 109 participants of iPrEx-OLE.

RESULTS

In iPrEx, there were no significant differences in urine α1m, albuminuria, or proteinuria by treatment arm. In iPrEx-OLE, after 24 weeks on PrEP, urine α1m and proteinuria increased by 21% [95% confidence interval (CI): 10 to 33] and 18% (95% CI: 8 to 28), respectively. The prevalence of detectable α1m increased from 44% to 65% (P < 0.001) and estimated glomerular filtration rate declined by 4 mL/min/1.73 m (P < 0.001). There was no significant change in albuminuria (6%; 95% CI: -7% to 20%).

CONCLUSION

PrEP with TDF/FTC was associated with a statistically significant rise in urine α1m and proteinuria after 6 months, suggesting that PrEP may result in subclinical tubule dysfunction.

Hypophosphatemic Osteomalacia Associated with Adefovir-induced Fanconi Syndrome Initially Diagnosed as Diabetic Kidney Disease and Vitamin D Deficiency

A 68-year-old man with type 2 diabetes mellitus and chronic hepatitis B infection was referred to the nephrology department before planned surgery for hepatocellular carcinoma. He had been receiving low-dose adefovir dipivoxil (ADV) for 11 years. Laboratory findings revealed impaired re-absorption in the proximal renal tubules. He had been diagnosed with diabetic kidney disease and osteomalacia due to vitamin D deficiency; thus, ADV was not discontinued until he was referred to us. In this case, concomitant diabetes mellitus and vitamin D deficiency might have prevented the early diagnosis of ADV-induced Fanconi syndrome.

Clinical Pharmacology in HIV Therapy

The success of combination antiretroviral therapy in the treatment of HIV-1-positive individuals has shifted clinical attention toward combination antiretroviral drug regimens that optimize tolerability, long-term safety, and durable efficacy. Wherever patients have access to treatment, morbidity and mortality are increasingly driven by non-HIV-associated comorbidities, which may be observed earlier than in age-matched controls and despite the best available combination antiretroviral therapy. Similarly, HIV-1-positive individuals are now diagnosed and treated earlier with anticipated lifelong therapy. The contribution of specific antiretroviral agents to long-term morbidity and mortality is dependent on the pharmacologic characteristics of these agents, and it is increasingly important in this context.

Pharmacology of Antiretrovirals in the Female Genital Tract for HIV Prevention

Preexposure prophylaxis (PrEP) is a powerful tool that, as part of a comprehensive prevention package, has potential to significantly impact the HIV epidemic. PrEP effectiveness is believed to be dependent on the exposure and efficacy of antiretrovirals at the site of HIV transmission. Clinical trial results as well as modeling and simulation indicate the threshold of adherence required for PrEP efficacy of emtricitabine/tenofovir disoproxil fumarate may differ between sites of HIV transmission with less forgiveness for missed doses in women exposed through genital tissue compared to people exposed through colorectal tissue. This suggests a role for local and host factors to influence mucosal pharmacology. Here we review the mucosal pharmacology of antiretrovirals in the female genital tract and explore potential determinants of PrEP efficacy. Host factors such as inflammation, coinfections, hormonal status, and the vaginal microbiome will be explored as well as the role of drug-metabolizing enzymes and transporters in regulating local drug exposure. The use of preclinical and early clinical models to predict clinical effectiveness is also discussed.

Pharmacokinetics of Tenofovir Alafenamide, Tenofovir, and Emtricitabine Following Administration of Coformulated Emtricitabine/Tenofovir Alafenamide in Healthy Japanese Subjects

A fixed-dose combination of tenofovir alafenamide (TAF) and emtricitabine (FTC) is available in 2 tablet strengths in Japan (FTC/TAF 200/10 mg and FTC/TAF 200/25 mg). These are used once daily in combination with other antiretroviral agents for the treatment of human immunodeficiency virus type 1 infection. The primary objective of this study was to investigate if there is any clinically relevant pharmacokinetic difference for TAF, tenofovir (TFV), and FTC between Japanese and non-Japanese with historical data. Three treatment groups were set in the study; FTC/TAF 200/10 mg in combination with darunavir (DRV) 800 mg + ritonavir (RTV) 100 mg (treatment A) or DRV/cobicistat (COBI) 800/150 mg (treatment B) and FTC/TAF 200/25 mg alone (treatment C). Especially for treatment C, it was designated for another purpose to evaluate the pharmacokinetic boosting effects of RTV and COBI on TAF bioavailability. As a result, the mean exposure of TAF among treatment groups was 125 to 154 ng/mL for C_max and 119 to 179 ng·h/mL for AUC_inf , which were comparable with the historical data in non-Japanese. The exposures of TFV and FTC were also consistent with the historical data. Therefore, no clinically relevant pharmacokinetic differences for TAF, TFV, and FTC were observed between Japanese and non-Japanese. Boosting effects of RTV and COBI on TAF bioavailability were slightly lower than we expected, less than a 2.5-fold increase, but it was within the range of exposures associated with efficacy and safety in phase 3 studies. Therefore, it was not considered clinically relevant.

Serum NGAL can act as an early renal safety biomarker during long-term nucleos(t)ide analogue antiviral therapy in chronic hepatitis B

Tubular renal toxicity is a side-effect of long-term therapy with nucleos(t)ide analogue(s) (NA) in chronic hepatitis B (CHB). There are no established surrogate markers in plasma of early NA-related toxicity. Neutrophil gelatinase-associated lipocalin (NGAL) is a protein produced by tubular cells following renal damage. We aimed therefore to retrospectively compare conventional renal markers (estimated glomerular filtration rates (eGFR) and urinary protein/creatinine ratio uPCR) with a sensitive biomarker (NGAL) in CHB patients on long-term NA therapy and assess the ability of new markers to predict NA-related renal toxicity (new onset of nonalbumin proteinuria). A total of 192 naïve CHB patients (median age 41 years, 78% males, 25% HBeAg+, 35% cirrhosis) were NA treated for at least 5 years (median 8.34 years, range 5.54-11.1 years). The eGFR and uPCR were compared at baseline and last clinical visit with serum NGAL concentrations measured by ELISA at same time-points and assessed according to the presence/absence of nonalbumin proteinuria at last visit. While baseline and last visit eGFR were similar (median:78 vs 84 mL/min), serum NGAL concentrations increased during therapy (median:9.4 vs 16.4 ng/mL, P < .05). The proportion of patients with proteinuria (uPCR > 15) increased between baseline and last visit (4.6% vs 21.4%, P < .05), with 30 (16%) patients having de novo nonalbumin proteinuria at last visit. High baseline NGAL concentrations were exclusive to patients with de novo nonalbumin proteinuria (median:31.7 vs 7.8 ng/mL, P < .01) and baseline NGAL levels >25 mg/mL were predictive of nonalbumin proteinuria at last visit (AUROC = 0.813). In conclusion, serum NGAL can act as a surrogate marker of early renal injury (de novo nonalbumin proteinuria) in CHB on long-term NA therapy.

The effect of HIV infection on glycaemia and renal function in type 2 diabetic patients

BACKGROUND

Infection with, and treatment of HIV is associated with effects on glycaemia and renal function. The purpose of this study was therefore to compare glycaemic control and albuminuria in HIV-positive and HIV-negative type 2 diabetic patients.

MATERIALS AND METHODS

Diabetic patients with and without HIV infection were recruited from a diabetic clinic at Chris Hani Baragwanath Hospital in Soweto, South Africa. Data was collected on weight, height, HbA1c, fasting glucose, urine albumin:creatinine ratio, HIV status, CD4 counts, viral load and concomitant therapies. Multivariable regression analysis was used to isolate the determinants of fasting glucose and HbA1c levels and risk factors for albuminuria.

RESULTS

Data were collected from 106 HIV-positive and 214 HIV-negative diabetics. All HIV infected subjects were receiving anti-retroviral therapy. The determinants of fasting glucose levels (log) were HIV infection (β = 0.04, p = 0.01) and use of anti-hypertensive agents (β = 0.07, p = 0.0006), whilst for HbA1c levels (log) they were HIV infection (β = -0.03, p = 0.03), BMI (β = 0.004, p = 0.0005), statin use (β = 0.04, p = 0.002) and glucose levels (β = 0.01, p<0.0005). In HIV-positive subjects, CD4 counts were negatively associated with glucose levels (β = -0.0002, p = 0.03). The risk factors for albuminuria were (odds ratio [95% CIs]) dyslipidaemia (1.94 [1.09, 3.44], p = 0.02) and HbA1c levels (1.24 [1.12, 1.38], p<0.0001).

DISCUSSION

These data suggest that glycaemic control is worse in type 2 diabetic subjects with HIV infection and that HbA1c underestimates glycaemia in these patients. Albuminuria was not associated with HIV-positivity. The negative relationship of CD4 counts with glucose levels may reflect viral removal and easing of the associated inflammatory response. It is possible that the association of statin and anti-hypertensive therapies with high HbA1c and glucose levels, respectively, is due to such therapies being given largely to subjects with poor glycaemic control.

Renal Impairment in Chronic Hepatitis B: A Review

The liver plays a key role in the metabolism of proteins. Liver dysfunction affects many organs because it communicates with the spleen and all digestive organs through the portal vein. Additionally, the kidney is an organ that is closely related to the liver and is involved in liver diseases. Glomerulonephritis is an important extrahepatic manifestation of chronic hepatitis B virus (HBV) infection. Nucleos(t)ide analog (NA) therapy effectively suppresses HBV replication by inhibiting HBV polymerase, thus decreasing the levels of serum HBV-DNA and delaying the progression of cirrhosis. Although NA therapy is recommended for all patients with chronic HBV infection, regardless of the level of renal dysfunction, there is limited information on NA use in patients with chronic kidney disease. In addition, in patients with end-stage liver cirrhosis, hepatorenal syndrome can be fatal. Hence, we should take into account the stage of impaired renal function in patients with cirrhosis. The aims of this article are to review the epidemiology, clinical presentation, treatment, and prevention of HBV-associated nephropathy.

Decreased expression of megalin and cubilin and altered mitochondrial activity in tenofovir nephrotoxicity

Tenofovir disoproxil fumarate (TDF) is a commonly used antiretroviral drug for HIV, rarely causing Fanconi syndrome and acute kidney injury. We retrospectively analyzed the clinico pathological presentation of 20 cases of tenofovir-induced tubulopathy, and investigated the renal expression of the megalin and cubilin proteins, as well as the mitochondrial respiratory chain activity. Estimated glomerular filtration rate (eGFR) before TDF exposure was 92 ml/min/1.73m², decreasing to 27.5 ml/min/1.73m² at the time of biopsy, with 30% of patients requiring renal replacement therapy. Proximal tubular expression of megalin and cubilin was altered in 19 and 18 cases, respectively, whereas it was preserved in patients exposed to TDF without proximal tubular dysfunction and in HIV-negative patients with acute tubular necrosis. Loss of megalin/cubilin was correlated with low eGFR and high urine retinol binding protein at the time of biopsy, low eGFR at last follow-up, and was more severe in patients with multifactorial toxicity. Patients with additional nephrotoxic conditions promoting tenofovir accumulation showed a lower eGFR at presentation and at last follow-up, and more severe lesions of acute tubular necrosis, than those with isolated tenofovir toxicity. Altered mitochondrial COX activity in proximal tubules was observed and may be an early cellular alteration in tenofovir nephrotoxicity. In conclusion, altered megalin/cubilin expression represents a distinctive feature in tenofovir-induced tubulopathy, and its severity is correlated with urine retinol binding protein loss and is associated with a poor renal prognosis. Concomitant exposure to other nephrotoxic conditions severely impacts the renal presentation and outcome.

Concomitant AIDS cholangiopathy and Fanconi syndrome as complications of HIV in a single patient

We describe the case of a 50-year-old woman presenting to our acute medicine department with generalised non-specific symptoms on a background of HIV managed on triple therapy (tenofovir, lamivudine and zidovudine). On admission, she was noted to be acidotic with proteinuria, glycosuria, hypophosphataemia and generalised body pain, and was diagnosed with Fanconi's renotubular syndrome secondary to tenofovir. It was also noted that she had elevated liver dysfunction markers, and an MRI of the liver revealed a focal stricture near the ampulla of Vater, resulting in a diagnosis of AIDS cholangiopathy. These two diagnoses are rare complications of HIV, and the presence of both these pathologies in a single patient has never been reported in the literature before, and we therefore believe that this case is the first of its kind.

Tenofovir-induced toxicity in renal proximal tubular epithelial cells: involvement of mitochondria

OBJECTIVE

In-vivo studies suggest that mitochondria is involved in tenofovir (TFV)-induced renal toxicity, but the underlying mechanisms are still unclear. The aim of the present study was to assess the effects of TFV and its prodrug, TFV disoproxil fumarate, on mitochondrial function and cell survival/viability in a renal proximal tubular cell line.

DESIGN AND METHODS

We evaluated parameters of cellular proliferation/survival (cell count, cell cycle, viability) and mitochondrial function (oxygen consumption, mitochondrial membrane potential, reactive oxygen species production) in NRK-52E cells. Intracellular TFV was measured by HPLC and expression of antioxidant genes was analysed by real-time PCR.

RESULTS

Similar intracellular levels of TFV were reached with lower concentrations of the prodrug than of the drug, and correlated directly with a decrease in cell number. Both compounds inhibited proliferation and compromised mitochondrial function by decreasing mitochondrial membrane potential and increasing oxygen consumption and mitochondrial superoxide production. Altered oxidative status was confirmed by the overexpression of antioxidant genes.

CONCLUSIONS

Intracellular accumulation of TFV induces mitochondrial toxicity in an in-vitro renal model and alters cell proliferation and viability. Our findings call for caution regarding the use of this nucleotide analogue reverse transcriptase inhibitor in patients with other risk factors that compromise mitochondrial function in the kidney.

Xenobiotic transporters and kidney injury

Renal proximal tubules are targets for toxicity due in part to the expression of transporters that mediate the secretion and reabsorption of xenobiotics. Alterations in transporter expression and/or function can enhance the accumulation of toxicants and sensitize the kidneys to injury. This can be observed when xenobiotic uptake by carrier proteins is increased or efflux of toxicants and their metabolites is reduced. Nephrotoxic chemicals include environmental contaminants (halogenated hydrocarbon solvents, the herbicide paraquat, the fungal toxin ochratoxin, and heavy metals) as well as pharmaceuticals (certain beta-lactam antibiotics, antiviral drugs, and chemotherapeutic drugs). This review explores the mechanisms by which transporters mediate the entry and exit of toxicants from renal tubule cells and influence the degree of kidney injury. Delineating how transport proteins regulate the renal accumulation of toxicants is critical for understanding the likelihood of nephrotoxicity resulting from competition for excretion or genetic polymorphisms that affect transporter function.

Nucleotide Reverse Transcriptase Inhibitors: A Thorough Review, Present Status and Future Perspective as HIV Therapeutics

BACKGROUND

Human immunodeficiency virus type-1 (HIV-1) infection leads to acquired immunodeficiency syndrome (AIDS), a severe viral infection that has claimed approximately 658,507 lives in the US between the years 2010-2014. Antiretroviral (ARV) therapy has proven to inhibit HIV-1, but unlike other viral illness, not cure the infection.

OBJECTIVE

Among various Food and Drug Administration (FDA)-approved ARVs, nucleoside/ nucleotide reverse transcriptase inhibitors (NRTIs) are most effective in limiting HIV-1 infection. This review focuses on NRTIs mechanism of action and metabolism.

METHODS

A search of PubMed (1982-2016) was performed to capture relevant articles regarding NRTI pharmacology.

RESULTS

The current classical NRTIs pharmacology for HIV-1 prevention and treatment are presented. Finally, various novel strategies are proposed to improve the efficacy of NRTIs, which will increase therapeutic efficiency of present-day HIV-1 prevention/treatment regimen.

CONCLUSION

Use of NRTIs will continue to be critical for successful treatment and prevention of HIV-1.

Assessment of the effect of antiretroviral therapy on renal and liver functions among HIV-infected patients: a retrospective study

Background

The emergence of highly active antiretroviral therapy (HAART) has dramatically improved quality of life in prolonging survival of human immunodeficiency virus (HIV)-infected patients on treatment in developed as well as developing countries. However, the main shortcoming of HAART in long-term use is its potential to cause liver and kidney derangements that may be life threatening. The drugs are actively accumulated in the proximal renal tubule resulting in functional disturbance with mitochondrial injury being one of the most important targets recognized. Therefore, the aim of this study was to assess the adverse effects of HAART on kidney and liver functions among HIV-infected patients presenting to the University of Gondar Hospital, Ethiopia.

Materials and methods

An institution-based retrospective study was conducted from 2010 to 2015 on a subset of HIV-infected patients. Data were collected from the registration book of the University of Gondar Hospital antiretroviral clinic laboratory after checking the completeness of age, gender, creatinine, blood urea nitrogen, and alanine aminotransferase level. Data were entered and analyzed using SPSS version 20. Descriptive statistics, chi-square test, one-way analysis of variance, and logistic regression were done to determine associations. A P-value <0.05 was considered statistically significant.

Results

A total of 275 study subjects were included in the study. Of these, 62.2% were females, and the overall prevalence of chronic kidney disease (CKD) before and after treatment was 3.6% and 11.7%, respectively. A majority of the CKD patients were in stage 3 for patients after treatment. The overall prevalence of hepatotoxicity was 6.5% and 16.7% before and after treatment, respectively. A majority of the patients developed Grade 2 hepatotoxicity 66.7% and 65.2% before and after treatment, respectively. Binary and multiple logistic regression analysis indicated that the female gender was a risk factor for CKD.

Conclusion

The prevalence of nephrotoxicity and hepatotoxicity were high among patients who took HAART. Stage 3 nephrotoxicity and Grade 2 hepatotoxicity had the highest incidences of the total toxicities, and the female gender was a risk factor for nephrotoxicity. Further prospective studies are recommended to determine the effect of HAART and contributing factors.

Brincidofovir Is Not a Substrate for the Human Organic Anion Transporter 1: A Mechanistic Explanation for the Lack of Nephrotoxicity Observed in Clinical Studies

BACKGROUND

Brincidofovir (BCV) is an orally bioavailable lipid conjugate of cidofovir (CDV) with increased in vitro potency relative to CDV against all 5 families of double-stranded DNA viruses that cause human disease. After intravenous (IV) administration of CDV, the organic anion transporter 1 (OAT1) transports CDV from the blood into the renal proximal tubule epithelial cells with resulting dose-limiting nephrotoxicity.

OBJECTIVE

To study whether OAT1 transports BCV and to evaluate the pharmacokinetic and renal safety profile of oral BCV compared with IV CDV.

METHODS

The cellular uptake of BCV and its major metabolites was assessed in vitro. Renal function at baseline and during and after treatment in subjects in BCV clinical studies was examined.

RESULTS

In OAT1-expressing cells, uptake of BCV and its 2 major metabolites (CMX103 and CMX064) was the same as in mock-transfected control cells and was not inhibited by the OAT inhibitor probenecid. In human pharmacokinetic studies, BCV administration at therapeutic doses resulted in detection of CDV as a circulating metabolite; peak CDV plasma concentrations after oral BCV administration in humans were <1% of those observed after IV CDV administration at therapeutic doses. Analysis of renal function and adverse events from 3 BCV clinical studies in immunocompromised adult and pediatric subjects indicated little to no evidence of associated nephrotoxicity. Over 80% of subjects who switched from CDV or foscarnet to BCV experienced an improvement in renal function as measured by maximum on-treatment estimated glomerular filtration rate.

CONCLUSIONS

The lack of BCV uptake through OAT1, together with lower CDV concentrations after oral BCV compared with IV CDV administration, likely explains the superior renal safety profile observed in immunocompromised subjects receiving BCV compared with CDV.

Osteomalacia induced by long-term low-dose adefovir dipivoxil: Clinical characteristics and genetic predictors

CONTEXT

Adefovir dipivoxil (ADV) was an important cause of adult-onset hypophosphatemic osteomalacia. However, its clinical characteristics and mechanisms have not been well defined.

OBJECTIVE

The objective of the study was to summarize the clinical characteristics of ADV-induced osteomalacia and to explore the association between ADV-associated tubulopathy and polymorphisms in genes encoding drug transporters.

DESIGN, SETTING, PATIENTS, AND MAIN OUTCOME MEASURE

Seventy-six affected patients were clinically studied. The SLC22A6 and ABCC2 genes were screened and compared with healthy people from the HapMap.

RESULTS

Hypophosphatemia, high serum alkaline phosphatase (ALP) levels, hypouricemia, nondiabetic glycosuria, proteinuria, metabolic acidosis and high bone turnover markers were the main metabolic characteristics. Fractures and pseudofractures occurred in 39 patients. Stopping ADV administration, supplementing calcitriol and calcium was effective during the follow-up period. Single SNP analysis revealed a higher percentage of the G/A genotype at c.2934 in exon 22 of the ABCC2 gene (rs3740070) in patients than in healthy people (12% [7 of 58 patients] vs. 0% [0 of 45 patients]; P=0.017), while there was no subject with homozygosity for the A allele at c.2934.

CONCLUSIONS

ADV can be nephrotoxic at a conventional dosage. The G/A genotype at c.2934 of the ABCC2 gene may be a predictor of patients at greater risk for developing ADV-associated tubulopathy. Larger case-control studies are needed to further verify this finding.

Tenofovir and kidney transplantation: case report

Background: Hepatitis B viral infection (HBV) has been regarded as a contraindication for kidney transplantation because of the high risk of viral activation induced by immunosuppressive therapy. Anti-retroviral drugs have changed the prognosis of patients with hepatitis B viral infection (HBV+) who are candidates for renal transplant; indeed, therapy with antiretroviral drugs may ensure lower rates of morbidity and mortality compared to traditional therapies. Entecavir is the first-line antiviral therapy recommended for the treatment of HBV+ kidney-transplanted patients. In case of resistance to entecavir, tenofovir may be an alternative drug, either alone or in combination with entecavir. However, the best strategy of treatment is still unknown. In this case-report, a HBV+ kidney-transplanted patient who presented resistance to entecavir was initially treated by associating tenofovir to entecavir and with tenofovir alone afterward. This strategy induced complete remission of viral replication. Case presentation: In a HBV+ kidney-transplanted patient under monotherapy with entecavir, HBV flare (HBV DNA > 170.000 × 10³ UI/mL, HBeAg+, HbeAb–) occurred 9 months after transplantation; at that time, blood chemistry highlighted: creatinine 1.46 mg/dL, blood urea 65 mg/dL, e-GFR 50 mL/min, proteinuria 300 mg/24 h, calciuria 2,12 mmol/24 h, phosphaturia 0.56 g/24 h, vitamin D 11.5 ng/mL, PTH 130 pg/mL, calcemia 2.3 mmol/L, and phosphoremia 2 mg/dL. Liver elastometry (FibroScan) showed moderate fibrosis. Tenofovir was associated to entecavir. Three months after the combination therapy, reduction in HBV DNA replication (351 × 10³ UI/mL) was obtained. Creatinine and e-GFR were 1.48 mg/dL and 52 mL/min, respectively. At this point, entecavir was discontinued. After 13 months of tenofovir monotherapy, complete remission of viral replication was achieved but renal function deteriorated and proteinuria increased. Conclusion: This case-report indicates that tenofovir is effective in reducing viral replication of hepatitis B virus in a kidney-transplanted patient who presented resistance to previous treatment with entecavir. However, it should be taken into account that tenofovir could affect renal function.

Polymorphisms associated with renal adverse effects of antiretroviral therapy in a Southern Brazilian HIV cohort

OBJECTIVE

This study evaluated the impact of seven single nucleotide polymorphisms in five candidate genes (ABCB1, ABCC2, ABCC4, SLC22A6, and SLC22A11) in relation to nephrotoxicity associated with highly active antiretroviral therapy (HAART) in HIV-infected individuals.

METHODS

The following single nucleotide polymorphisms were genotyped by real-time PCR: ABCB1 rs1045642, ABCC2 rs717620 and rs2273697, ABCC4 rs1751034 and rs3742106, SLC22A6 rs11568626, and SLC22A11 rs11231809 in 507 HIV-infected patients from the city of Porto Alegre, Southern Brazil, receiving HAART for, at least, 1 year.

RESULTS

From the 507 HIV-infected patients recruited, 19.1% presented a reduction in estimated glomerular filtration rate (eGFR). A total of 16 (3.2%) patients fulfilled the criteria for chronic kidney disease (defined as eGFR<60 ml/min/1.73 m). Individuals carrying at least one T allele of ABCC2 -24 C>T (rs717620) presented lower eGFR than C/C homozygotes (104 ± 22 vs. 108 ± 22 ml/min/1.73 m, independent-samples t-test, P=0.040). In multivariate analysis, the predictors associated with decreased eGFR were time of treatment, tenofovir use, atazanavir/ritonavir use, and carrying one T allele of ABCC2 -24 C>T.

CONCLUSION

Our data support the importance of genetic factors in the etiology of nephrotoxicity in patients treated with HAART. Studies to verify treatment implications of genotyping before HAART initiation may be advisable to guide the selection of an appropriate antiretroviral therapy regimen.

HIV Infection, Tenofovir, and Urine α1-Microglobulin: A Cross-sectional Analysis in the Multicenter AIDS Cohort Study

BACKGROUND

Tenofovir disoproxil fumarate (TDF) can cause proximal tubular damage and chronic kidney disease in human immunodeficiency virus (HIV)-infected individuals. Urine α1-microglobulin (A1M), a low-molecular-weight protein indicative of proximal tubular dysfunction, may enable earlier detection of TDF-associated tubular toxicity.

STUDY DESIGN

Cross-sectional.

SETTING & PARTICIPANTS

883 HIV-infected and 350 -uninfected men enrolled in the Multicenter AIDS Cohort Study.

PREDICTORS

HIV infection and TDF exposure.

OUTCOME

Urine A1M level.

RESULTS

Urine A1M was detectable in 737 (83%) HIV-infected and 202 (58%) -uninfected men (P<0.001). Among HIV-infected participants, 573 (65%) were current TDF users and 112 (13%) were past TDF users. After multivariable adjustment including demographics, traditional kidney disease risk factors, and estimated glomerular filtration rate, HIV infection was associated with 136% (95% CI, 104%-173%) higher urine A1M levels and 1.5-fold (95% CI, 1.3- to 1.6-fold) prevalence of detectable A1M. When participants were stratified by TDF exposure, HIV infection was associated with higher adjusted A1M levels, by 164% (95% CI, 127%-208%) among current users, 124% (95% CI, 78%-183%) among past users, and 76% (95% CI, 45%-115%) among never users. Among HIV-infected participants, each year of cumulative TDF exposure was associated with 7.6% (95% CI, 5.4%-9.9%) higher A1M levels in fully adjusted models, a 4-fold effect size relative to advancing age (1.8% [95% CI, 0.9%-2.7%] per year). Each year since TDF treatment discontinuation was associated with 4.9% (95% CI, -9.4%--0.2%) lower A1M levels among past users.

LIMITATIONS

Results may not be generalizable to women.

CONCLUSIONS

HIV-infected men had higher urine A1M levels compared with HIV-uninfected men. Among HIV-infected men, cumulative TDF exposure was associated with incrementally higher A1M levels, whereas time since TDF treatment discontinuation was associated with progressively lower A1M levels. Urine A1M appears to be a promising biomarker for detecting and monitoring TDF-associated tubular toxicity.

Incidence of stage 3 chronic kidney disease and progression on tenofovir-based regimens

OBJECTIVE

To describe the incidence of rapid kidney function decline (RKFD), and stage 3 chronic kidney disease (CKD) in HIV-1-infected adults initiated on tenofovir-containing antiretroviral therapy.

METHODS

A retrospective cohort study at the infectious diseases clinic of Tygerberg Academic Hospital in Cape Town, South Africa. Patients with more than 3 ml/min per year decline in estimated glomerular filtration were classified as having RKFD, and stage 3 CKD was defined as a value less than 60 ml/min per 1.73 m. We used logistic and Cox proportional hazards regression models to determine factors associated with RKFD and stage 3 CKD.

RESULTS

Of 650 patients, 361 (55%) experienced RKFD and 15 (2%) developed stage 3 CKD during a median interquartile range follow-up time of 54 (46.6-98) weeks. For every 10-year increase in age and 10 ml/min lower baseline estimated glomerular filtration, the odds of RKFD increased by 70% [adjusted odds ratio = 1.70, 95% confidence interval (CI) 1.36-2.13] and 57% (adjusted odds ratio = 1.57, 95% CI 1.38-1.80), respectively. Each 10-year older age was associated with a 1.90-fold increased risk of developing stage 3 CKD (adjusted hazard ratio = 1.90, 95% CI: 1.10-3.29). Women had about four-fold greater risk of stage 3 CKD compared with men (adjusted hazard ratio = 3.96, 95% CI: 1.06-14.74).

CONCLUSION

About half of our study population developed RKFD but only 2% progressed to stage 3 CKD. Approaches that provide balanced allocation of limited resources toward screening and monitoring for kidney dysfunction and HIV disease management are critically needed in this setting.

Evaluation of Drug-Drug Interactions between Direct-Acting Anti-Hepatitis C Virus Combination Regimens and the HIV-1 Antiretroviral Agents Raltegravir, Tenofovir, Emtricitabine, Efavirenz, and Rilpivirine

The three direct-acting antiviral agent (3D) regimen is a novel combination of direct-acting antiviral agents (DAAs) that has proven effective for the treatment of hepatitis C virus (HCV) infection. Given the potential for coadministration in patients with human immunodeficiency virus infection, possible drug interactions with antiretroviral drugs must be carefully considered. Four phase 1, multiple-dose pharmacokinetic studies were conducted in healthy volunteers (n = 66). The 3D regimen of 150/100 mg daily paritaprevir/ritonavir, 25 mg daily ombitasvir, and 400 mg twice-daily dasabuvir was administered alone or in combination with 200 mg daily of emtricitabine and 300 mg daily of tenofovir disoproxil fumarate (tenofovir DF), 25 mg daily of rilpivirine, or 400 mg of raltegravir twice daily. A 2-DAA regimen of 150/100 mg daily paritaprevir/ritonavir and 400 mg of dasabuvir twice daily was also studied in combination with efavirenz/emtricitabine/tenofovir DF at 600/200/300 mg daily, respectively (Atripla; Bristol-Myers Squibb). Pharmacokinetic parameters were determined from plasma drug concentrations. No clinically significant drug interactions were observed (≤32% change in exposure) between the 3D regimen and that of emtricitabine plus tenofovir DF. Raltegravir exposure was increased up to 134% when the drug was coadministered with the 3D regimen. Although coadministration with rilpivirine was well tolerated in healthy volunteers, observed elevations in rilpivirine exposures may increase the potential for adverse drug reactions. Concomitant use of the 2-DAA regimen and efavirenz/emtricitabine/tenofovir DF was discontinued owing to poor tolerability and adverse events. No dose adjustment is required during coadministration of raltegravir, tenofovir DF, or emtricitabine with the 3D regimen. Rilpivirine is not recommended and efavirenz is contraindicated for coadministration with the 3D regimen.

A Single-Nucleotide Polymorphism in ABCC4 Is Associated with Tenofovir-Related Beta2-Microglobulinuria in Thai Patients with HIV-1 Infection

Background

In Thailand, the combined generic anti-retroviral drug stavudine/lamivudine/nevirapine (d4T/3TC/NVP) has been used to treat human immunodeficiency virus (HIV)-infected individuals since 2001. Due to relatively frequent adverse effects, d4T gradually has been replaced with tenofovir disoproxil fumarate (TDF). Although the frequency of adverse drug effects with TDF is lower than that with d4T, TDF is known to induce kidney dysfunction, especially in the proximal tubules. It has been reported that renal tubular transporters, including members of the multi-drug resistant (MDR) protein family, are implicated in tenofovir extrusion and may, therefore, confer susceptibility to TDF-induced kidney tubular dysfunction (KTD). We have explored the association between KTD and polymorphisms in genes that encode adenosine triphosphate-binding cassette (ABC)-type MDRs.

Methods

HIV-infected patients receiving TDF-containing antiretroviral regimens for at least one year were enrolled in the study. The levels of beta2-microglobulin in urine and creatinine (Cr) were measured. Three single-nucleotide polymorphisms, ABCC2 C-24T (rs717620), ABCC2 G1429A (rs2273697), and ABCC4 T4976C (rs1059751), were analyzed using TaqMan SNP genotyping assays.

Results

A total of 273 HIV-infected patients were recruited. The median number of years of TDF treatment was 5.04 with interquartile range (IQR) of 3.9–6.7. Despite the length of treatment with TDF, 98.5% patients maintained an estimated glomerular filtration rate (eGFR) of >60 mL/min as calculated by the CKD-EPI formula. Fifty-four patients (19.8%) showed beta2-microglobulinuria (median 2636 μg/g Cr with IQR of 1519–13197 μg/g Cr). The allele frequency of ABCC4 T4976C among those 54 patients was 0.602, compared to 0.475 among the 219 remaining patients (p = 0.018).

Conclusions

Approximately 20% of HIV-infected patients receiving TDF showed beta2-microglobulinuria. The C allele at position 4976 of the ABCC4 gene was associated with beta2-microglobulinuria in this population. This polymorphism may help to identify patients at greater risk for developing TDF-associated KTD.

Differential Mechanisms of Tenofovir and Tenofovir Disoproxil Fumarate Cellular Transport and Implications for Topical Preexposure Prophylaxis

Intravaginal rings releasing tenofovir (TFV) or its prodrug, tenofovir disoproxil fumarate (TDF), are being evaluated for HIV and herpes simplex virus (HSV) prevention. The current studies were designed to determine the mechanisms of drug accumulation in human vaginal and immune cells. The exposure of vaginal epithelial or T cells to equimolar concentrations of radiolabeled TDF resulted in over 10-fold higher intracellular drug levels than exposure to TFV. Permeability studies demonstrated that TDF, but not TFV, entered cells by passive diffusion. TDF uptake was energy independent but its accumulation followed nonlinear kinetics, and excess unlabeled TDF inhibited radiolabeled TDF uptake in competition studies. The carboxylesterase inhibitor bis-nitrophenyl phosphate reduced TDF uptake, suggesting saturability of intracellular carboxylesterases. In contrast, although TFV uptake was energy dependent, no competition between unlabeled and radiolabeled TFV was observed, and the previously identified transporters, organic anion transporters (OATs) 1 and 3, were not expressed in human vaginal or T cells. The intracellular accumulation of TFV was reduced by the addition of endocytosis inhibitors, and this resulted in the loss of TFV antiviral activity. Kinetics of drug transport and metabolism were monitored by quantifying the parent drugs and their metabolites by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Results were consistent with the identified mechanisms of transport, and the exposure of vaginal epithelial cells to equimolar concentrations of TDF compared to TFV resulted in ∼40-fold higher levels of the active metabolite, tenofovir diphosphate. Together, these findings indicate that substantially lower concentrations of TDF than TFV are needed to protect cells from HIV and HSV-2.

Safety of oral tenofovir disoproxil fumarate-based pre-exposure prophylaxis for HIV prevention

INTRODUCTION

Tenofovir disoproxil fumarate (TDF)-based pre-exposure prophylaxis is a novel HIV prevention strategy for individuals at increased sexual risk for HIV infection. For any biomedical prevention intervention, the bar for tolerating adverse effects in healthy persons is high compared to therapeutic interventions.

AREAS COVERED

We provide a concise summary of the clinical safety of TDF-based pre-exposure prophylaxis with focus on TDF-related effects on tolerability, kidney function, bone density, HIV resistance, sexual and reproductive health. The evidence base for this review is derived from a literature search of both randomized and observational studies evaluating efficacy and safety of TDF-based PrEP, TDF alone or in combination with emtricitabine, identified from PUBMED and EMBASE electronic databases, clinicaltrials.gov and major HIV conferences.

EXPERT OPINION

TDF-based pre-exposure prophylaxis is a potent intervention against HIV acquisition when taken which is generally safe and well tolerated. The risk of the small, non-progressive, and reversible decline in glomerular filtration rate and bone mineral density as well as the potential selection for drug resistance associated with PrEP are outweighed, at the population level and broadly for individuals, by PrEP's substantial reduction in the risk of HIV infection.

[Management of hepatitis B virus and hepatitis C virus infection in chronic kidney failure]

Chronic infections by hepatitis B (HBV) and C virus (HCV) result in diagnosis and therapeutic issues in dialysis and kidney recipients patients. The exposure to nosocomial, including blood transfusion, risk explains the high prevalence of HBV and HCV infection in this setting. Chronic infection reduces the survival of both patients and allografts, including a specific risk of de novo glomerulonephritis. Cirrhosis was considered as a contra-indication to renal transplantation given the high risk of decompensation and death, questionning the indication of a combined liver and kidney transplantation. Thus, it is mandatory to screen HBV and HCV markers in all dialysis patients, whether or not they are candidates to transplantation. Liver biopsy allows evaluating the severity of the liver disease since the noninvasive markers of fibrosis appear to be less accurate in "renal" patients than in the general population and to better define antiviral therapeutic indications. HCV treatment was mainly based on pegylated interferon α (and low doses of ribavirin), which is contra-indicated in kidney recipients given the risk of graft rejection; HCV treatment is now based on the use of oral direct acting antivirals, which are very potent and well tolerated. HBV replication is now easily suppressed by second-generation nucleos(t)tidic analogues (entecavir and tenofovir), which will be indicated in all the dialysis patients with significant fibrosis (F2,3 or 4 according to the Metavir scoring system) and in any candidate to renal transplantation and to any HBsAg-positive kidney recipients. The best treatment remains preventive by anti-HBV vaccination for HBV and by the respect of universal hygiene rules for HCV.

A Quantitative Approach to Screen for Nephrotoxic Compounds In Vitro

Nephrotoxicity due to drugs and environmental chemicals accounts for significant patient mortality and morbidity, but there is no high throughput in vitro method for predictive nephrotoxicity assessment. We show that primary human proximal tubular epithelial cells (HPTECs) possess characteristics of differentiated epithelial cells rendering them desirable to use in such in vitro systems. To identify a reliable biomarker of nephrotoxicity, we conducted multiplexed gene expression profiling of HPTECs after exposure to six different concentrations of nine human nephrotoxicants. Only overexpression of the gene encoding heme oxygenase-1 (HO-1) significantly correlated with increasing dose for six of the compounds, and significant HO-1 protein deregulation was confirmed with each of the nine nephrotoxicants. Translatability of HO-1 increase across species and platforms was demonstrated by computationally mining two large rat toxicogenomic databases for kidney tubular toxicity and by observing a significant increase in HO-1 after toxicity using an ex vivo three-dimensional microphysiologic system (kidney-on-a-chip). The predictive potential of HO-1 was tested using an additional panel of 39 mechanistically distinct nephrotoxic compounds. Although HO-1 performed better (area under the curve receiver-operator characteristic curve [AUC-ROC]=0.89) than traditional endpoints of cell viability (AUC-ROC for ATP=0.78; AUC-ROC for cell count=0.88), the combination of HO-1 and cell count further improved the predictive ability (AUC-ROC=0.92). We also developed and optimized a homogenous time-resolved fluorescence assay to allow high throughput quantitative screening of nephrotoxic compounds using HO-1 as a sensitive biomarker. This cell-based approach may facilitate rapid assessment of potential nephrotoxic therapeutics and environmental chemicals.

Reactivation of chronic hepatitis B during treatment with tenofovir disoproxil fumarate: drug interactions or low adherence?

We describe a case of a 61-year-old man with chronic hepatitis B, hepatitis B e antibody (HBeAb) positive, treated with tenofovir disoproxil fumarate (TDF), who developed virological and biochemical viremic reactivation with an increase in transaminase plasma levels. The patient's history revealed that he had discontinued TDF about 5 days before admission and, from December 2013, had been taking venlafaxine, paroxetine and zolpidem for some episodes of depression. Clinical evaluation and laboratory findings excluded the presence of systemic diseases that might have been able to explain the drug inefficacy, while pharmacological evaluation suggested a possible drug-drug interaction. In order to assess the possible occurrence of resistance, mutational analysis of hepatitis B virus (HBV) was performed and excluded the presence of resistance for TDF. TDF was prescribed, and venlafaxine, paroxetine and zolpidem were discontinued. The follow-up at 3, 6 and 12 months documented a good response to TDF with a time-related decrease of HBV-DNA and alanine aminotransferase.

Tenofovir: What We Have Learnt After 7.5 Million Person-Years of Use

Tenofovir was licensed for use in patients with HIV in 2001 and since then has become a firmly established anti-retroviral in both guidelines and routine practice. Data have been presented from many pivotal studies—informing on its efficacy, use, and adverse features—and there are also over 7.5 million patient-years of experience to date. We explore the data on this nucleotide reverse transcriptase inhibitor in HIV presented since 2008—focusing on efficacy, side effects, and utility.